CHEM 1442 1st Edition Lecture 4Outline of Last Lecture I. PolarizabilityII. Aqueous SolutionIII. Concentration UnitsIV. Chapter 16Outline of Current Lecture V. Colligative PropertiesVI. Vapor Pressure LoweringVII. Chapter 16Current LectureColligative PropertiesProperties associated with a substance: DensityDo properties stay the same as those of “pure” solvent when a solute is added? NO!Properties of a solvent changes.Does the change in property depend on how much solute is dissolved? YES!Does the change in property depend on the types of solutes? YES!*Change in properties depend on:- What solute- How much of solute- Which solvent* (not so important because most of the time it is water)*Change in colligative properties depends on:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- How much of solute- What solvent*Density is NOT a colligative propertyMelting Point is a colligative propertyMelting-Point Depression (Freezing-Point Depression)- The melting or freezing point of a “pure” solvent is always greater than that of a solutioncontaining the solvent- ∆Tf= Tof –Tf> 0- Tof is the freezing point of the pure solvent- Tf is the freezing point of the solution- This is always positive, because solution is always less than what you started with- The change in the freezing point depends only on the concentrations- ∆Tf = Kf x m- m is the molality- Kf is the molal freezing-point depression constant- Colligative property that does not depend on what kind of soluteBoiling-Point Elevation- ∆Tb = Tb –Tob> 0- Tob is the boiling point of the pure solvent- Tb is the boiling point of the solution- ∆Tb = Kb x m- m is the molality- Kbis the molalboiling-point elevation constantVapor Pressure LoweringUnder the assumption that the solute is “non-volatile”- Posolvent>Psolvent- Solute does not vaporize causing vapor pressure to decrease- Raoult’s Law: Psolvent = Xsolventx Posolvent- Xsolvent = mole fraction of solvent- ∆P= Posolvent–PsolventUnder the assumption that the solution is “volatile”- Posolvent<Psolvent+ Psolute- Psolvent = Xsolventx Posolvent- Psolute = Xsolutex